This invention relates generally to apparatus for use with windows and specifically for use with windows such as a casement window or an awning window having a sash which is adapted to be swung between closed and open positions.
Modern casement and awning windows usually are associated with a reversible rotary actuator which may be used to open and close the window sash. The actuator may include a hand crank adapted to be turned in one direction to open the sash and in the opposite direction to close the sash. Alternatively, the actuator includes a reversible electric motor which is associated with the sash in the manner disclosed in Lense U.S. Pat. No. 4,553,656.
Window actuators of the type which are presently used commercially are capable of being backdriven. That is to say, the actuator moves and permits movement of the sash when an external force such as wind is exerted on the sash. With such actuators, wind is capable of buffeting the sash and can cause noise and vibration as well as possible damage to the sash. In addition, an intruder can force the sash open by pulling on the sash and backdriving the actuator and thus the intruder may take advantage of a partially open sash to gain easy entry to the premises.